1. Field of the Invention
This invention relates to a process or method for killing roots and other living material within sewer lines, and in particular to a method for using a heated liquid as a thermal herbicide for killing these roots and living materials.
2. Description of the Prior Art
The growth of roots within sewer lines has long presented a major problem to the proper functioning of a sewage collection system. Roots depending from trees and other vegetation grow faster in a direction toward the moist areas surrounding joints or breaches in sewer line sections. These branches may be due to faults in the material forming the sewer line or due to defective couplings between sewer line sections. In any event, the roots penetrate through the breaches and into the interior cavity of the sewer line. Once inside the sewer line, the roots grow rapidly in order to fully absorb the moisture within the lines. The roots branch profusely causing large clumps or root masses which generally depend from the upper sections of the sewer lines. Root growth generally does not continue below the mean water line since the lack of oxygen within the sewage presents a hostile environment for the roots.
The hair-like roots are gradually covered with layer upon layer of fat or grease which is transported continually through the sewer lines. As the grease coating builds up on each of the hair-like roots, the spaces between the roots are filled. In this manner the net-like structure created by the hair-like roots agglomerates with the grease, thus presenting a substantial obstruction to the passage of sewage through the sewer lines. In extreme cases the accumulation of root growth and grease can completely block the upper sections of the sewer line, thereby inhibiting the sewage flow capacity.
Several different methods have been developed to control the roots within the sewer lines. The first type of method employs a toxic chemical, such as copper sulfate, which is applied directly to the roots within the sewer line. This method is often ineffective since it is difficult to remove the grease and other organic material covering the roots, a preliminary procedure which is necessary to allow the chemicals to penetrate the cutin and suberin layers of the root. These methods may prove dangerous to the environment in that the chemicals may leak from breaches in the sewer line and contaminate the surrounding soil, or in extreme cases an adjacent drinking water supply. Examples of the chemical method are disclosed by Horne in U.S. Pat. Nos. 3,741,807; 3,892,588; and 3,874,926; Weston in U.S. Pat. No. 2,976,191; Tharp in U.S. Pat. No. 2,763,288; Farage in U.S. Pat. No. 3,830,659; Hoff in U.S. Pat. No. 3,403,993; and Otterson in U.S. Pat. No. 1,274,931.
A second method of removing roots from sewer lines employs a mechanical cutter which is rotatably transported in a longitudinal direction through the sewer lines for severing the roots at their point of passage through the breach in the sewer line. These methods are generally unsatisfactory for several reasons. First, in many instances the cutting of the root induces an increased growth rate of the root, thereby exacerbating the problem rather than solving it. Second, the roots are generally soft and will merely bend when forced in communication with the cutting blade. Third, even if the diameter of the rotating blade is increased to communicate with the internal circumferential surface of the sewer line for severing the root adjacent to the breach in the line, the blade often binds within the sewer line. A cutter of this type is disclosed by Gray in U.S. Pat. No. 3,171,150. The Gray rooter apparatus is driven by steam which is expelled from the rotary cutter toward the roots to cauterize the severed root segment.